>The U.S.G. has never renounced first use of nuclear weapons, they have always kept it open as a possible "tactical" alternative.>
True, but this is also true of Britain, France and Pakistan. Russia has also withdrawn 'no first use pledge'. As for China and India: 'No first use pledge' is part of their nuclear doctrine, but whether they will really adhere to that pledge under crisis situation is uncertain.
Every nuclear weapon state without exception is committed to use nuclear weapons under certain conditions.
Ulhas